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ICES Marine Science Symposia ICES mar. Sei. Symp., 199: 459-467. 1995 Genetic differentiation in Berryteuthis magister from the North Pacific O. N. Katugin Katugin, O. N. 1995. Genetic differentiation in Berryteuthis magister from the North Pacific. - ICES mar. Sei. Symp., 199: 459-467. Berryteuthis magister is a widespread quasibenthic commercial squid from the North Pacific. Intraspecific genetic differentiation was determined by allozyme electrophore­ tic analysis. Eighteen sample lots (2100 individuals) from geographically separated North Pacific regions were subjected to allozyme electrophoretic analysis using a total of 14 enzymes and unidentified ganglion protein spectra with polymorphic zones. Four loci with variant allele frequencies greater than 0.05 were found to be useful for population studies. No significant violations of the Hardy-Weinberg equilibrium were found at any loci in the samples. There was no evidence of genetic differences between sexes. Analysis of genetic differentiation using Wright’s F-statistics, cluster analysis of genetic distances, and contingency chi-square analysis suggested that there are popu­ lation differences between squids from the three major geographical localities: the Sea of Japan, the Kurile-Komandor region, and the Gulf of Alaska. Genetic divergence between squid from the Kurile-Komandor part of the species range probably reflects subpopulation differentiation of local stocks from successive generations. O. N. Katugin: Pacific Research Institute o f Fisheries and Oceanography (TINRO), Vladivostok, 690 600, Russia [tel: (+7) 4232 25 7790, fax: (+7) 4232 25 7783], been investigated electrophoretically. This family is con­ Introduction sidered to be the most abundant group of cephalopods in During the last two decades biochemical genetic tech­ the subarctic waters of the Pacific Ocean where it pre­ niques based on electrophoretic separation of multiple sumably originated and diverged (Nesis, 1973). It com­ protein forms, especially enzymes, have uncovered a prises about 17-19 species in three genera (Nesis, 1982): great source of “cryptic” (non-morphological) variation Gonatus, Gonatopsis, and Berryteuthis. that exists in natural populations of a variety of taxa. Berryteuthis magister has a wide distribution range; Most polymorphisms at individual enzyme loci have adult squid dwell on the continental slope and in the appeared to be interpretable from a genetic standpoint near-shelf waters of the Sea of Japan, along the Kurile because of co-dominant inheritance of most of the allelic Chain, in the Sea of Okhotsk, across the Bering Sea, and isoenzymes (allozymes). Frequencies of electrophoreti- through the Gulf of Alaska down to California. The cally detectable allelic variants have been widely used in species is quasibenthic, and passes through three stages, animal population structure analysis, particularly of or ecological phases, in its orthogenesis: (1) planktonic invertebrates. Though many molluscan species have hatchlings and young juveniles in the epipelagic layers, been investigated by this approach, few studies have (2) micronectonic juveniles (descending phase), and (3) involved cephalopods. Most of the cephalopod studies nectobenthic adults (Kubodera, 1982). The species has a concerned myopsid squids of the family Loliginidae lifespan of about one or two years (Naito et al., 1977', (Ally and Keck, 1978; Christofferson et a i, 1978; Nat- Yuuki and Kitazawa, 1986; Okutani, 1988; Nesis, 1989). sukari etal., 1986; Augustyn and Grant, 1988; Carvalho The spawning period extends over nearly two months or andLoney, 1989; Garthwaite etal., 1989; Brierley etal., more, followed by the death of the spent squid. Biologi­ 1993b; Yeatman and Benzie, 1993), and oegopsid squids cal and fisheries data suggest that intraspecific variability of the family Ommastrephidae (Murata et al., 1985; exists in B. magister. Discrete groups with uncertain Smith et al., 1987; Carvalho et al., 1992; Brierley et al., populational status have been revealed by the analysis of dorsal mantle lengths, body weights, and stages of 1993a; Kim, 1993). Oegopsid squids of the family Gonatidae have not maturity (Fedorets, in press). Geographically isolated 460 O. N. Katugin ICES mar sd Symp 1W (ms) Table 1. Location, collection dates, sample sizes, and state of maturity for Berryteuthis magister. Location Coordinates Date N M Sea of Japan 1 Kitajamato Bank 39°50'N 133°44'E Oct., 1987 200 AI Kurile Islands 2 Southern Kuriles 44°30'N 147°50'E Feb., 1990 96 AI 3 Central Kuriles 47°04'N 152°20'E Sep., 1989 100 AI 4 Central Kuriles 47°02'N 152°14'E Feb., 1990 223 AR 5 Central Kuriles 47°01'N 152°16'E May, 1990 93 AR 6 Central Kuriles 47°02'N 152°37'E May, 1991 214 AR 7 Northern Kuriles 49°48’N 156°28'E Aug., 1988 99 AR 8 Northern Kuriles 49°43'N 155°20'E Aug., 1989 104 AR 9 Northern Kuriles 49°17'N 155°39'E Feb., 1990 100 AR 10 Northern Kuriles 49°28'N 155°36'E Sep., 1990 88 AI 11 Northern Kuriles 49°41'N 156°22'E Nov., 1991 63 AI Western Bering Sea 12 Komandor Islands 55°27'N 165°10'E Jul., 1988 107 AR 13 Komandor Islands 54°23'N 167°70'E Apr., 1989 100 AM 14 Komandor Islands 54°20'N 167°06'E May, 1989 100 AM 15 Komandor Islands 54°20'N 168°17'E Jan., 1990 94 AM 16 Komandor Islands 53°23'N 165°17'E May, 1990 95 AM 17 Navarin Bay 61°40'N 176°30'E Sep., 1990 160 AM Gulf of Alaska 18 Gulf of Alaska 57°23'N 155°15'W Mar., 1988 46 AI. AR N no. of specimens in a sample; M - maturity (AI — immature adults; AR = ripening adults; AM = mature adults). groups within the species are expected for the following reasons: (1) oceanographic conditions differ consider­ ably across the range; (2) certain geographic barriers, such as islands and shallow straits, occur across the range • 1 7 of the squid; (3) spawning grounds are presumably re­ 6 0 " stricted to some deepwater regions, though they have 18 not been determined precisely due to the difficulties of 50" trawling; (4) early life stages concentrate in several dis­ crete North Pacific areas, namely, in the southeastern 40" part of the Okhotsk Sea, in the central southern part of the Bering Sea, in the Gulf of Alaska (Kubodera and Jefferts, 1984), and in the Sea of Japan (Yuuki and Kitazawa, 1986). Since the 1970s the gonate squid B. magister has been the object of a commercial fishery. The annual catch by Figure 1. Locations from which samples of Berryteuthis magis-magis­ ter were taken. Numbers correspond to those in Table 1. the Russian fishing fleet in the waters near the Kurile Islands is about 70000 t (Fedorets, pers. comm.) and has been expanding. In order to establish reasonable com­ mercial management for this squid, it is necessary to Materials and methods determine the number of self-sustaining intraspecific Eighteen sample lots of B. magister were taken from groups, or breeding populations, that make up the scientific research catches during 1987-1990 by bottom species. For this purpose, selected enzymes from mantle trawling (Table 1, Fig. 1). A total of about 2100 squid tissue extracts, and general protein spectra from gang­ were frozen at — 20°C for electrophoretic investigation. lion tissue extracts were studied by electrophoresis in Individual mantle and ganglion tissue samples were starch and polyacrylamide gels. The revealed polymor­ prepared for analysis by standard techniques: about phic genetic loci were used to elucidate intraspecific 1 cm3 of tissue from every animal was homogenized with genetic differentiation in B. magister with regard to its an equal amount of distilled water and centrifuged at population structure. 8000g for 30 min at 0°C. Vertical electrophoresis in 5% ic e s mar. Sd. Symp., 199(1995) Genetic differentiation in Berryteuthis magister from the North Pacific 461 polyacrylamide gels in a continuous TRIS-EDTA Na2- contribution of samples, groups of samples, and individ­ borate (pH 8.4) buffer system (Peacock et al., 1965), and ual loci to the total level of genetic differentiation. horizontal electrophoresis in 14% starch gels in a con­ tinuous TRIS-maleate (pH 7.4) buffer system (Shaw and Prasad, 1970) were used to separate water-soluble pro­ Results teins from individual supernatants. Ganglion general protein spectra were revealed on polyacrylamide gels Eleven enzymes were stained and gave good interpre­ with Coomassie BB (G-250) in 12.5% TCA (Katugin, table electrophoretic banding patterns: glycerophos­ 1991). Enzymatic activity in mantle tissue extracts was phate dehydrogenase (locus Gpd), lactate dehydrogen­ revealed by histochemical staining protocols (Shaw and ase (two loci: Ldh-1, and Ldh-2), NAD-dependent Prasad, 1970; Harris and Hopkinson, 1976). malate dehydrogenase (locus M dh), NADP-dependent Alleles were designated according to the electrophor­ malate dehydrogenase (locus Me), isocitric dehydrogen­ etic mobilities of their products, relative to those of the ase (locus Idh), 6-phosphogluconate dehydrogenase most common allele (which was designated 100). Loci (locus Pgd), phosphoglucose isomerase (locus Pgi), for a particular enzyme were numbered in order of phosphoglucomutase (two loci: Pgm-1, and Pgm-2), decreasing electrophoretic mobility towards the anode, superoxide dismutase (locus Sod), esterase (two loci: and the slowest locus was assigned number 1. A locus Est-1, and Est-2), and acid phosphatase (locus Acp). was considered polymorphic if the frequency of the Fourteen presumptive structural loci were coding for common allele did not exceed 0.95 in at least one sample these enzymes. Electrophoretic variation was observed of squid. at the loci Gpd, Sod, and Est-2, but was not taken into Genotypic frequencies for each highly polymorphic account due to the accepted 95% criterion of polymor­ locus were examined for agreement with Hardy-Wein- phism. Three enzyme loci were sufficiently polymorphic berg expectations using a goodness-of-fit chi-square test.
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